From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Peter Hurley <peter@hurleysoftware.com>
Cc: Michal Nazarewicz <mina86@mina86.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-sh@vger.kernel.org,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: CMA: test_pages_isolated failures in alloc_contig_range
Date: Tue, 28 Oct 2014 20:59:58 +0200 [thread overview]
Message-ID: <1703418.04z9xDaRPF@avalon> (raw)
In-Reply-To: <544F9EAA.5010404@hurleysoftware.com>
Hello,
On Tuesday 28 October 2014 09:48:26 Peter Hurley wrote:
> [ +cc Andrew Morton ]
>
> On 10/28/2014 08:38 AM, Michal Nazarewicz wrote:
> > On Sun, Oct 26 2014, Laurent Pinchart wrote:
> >> Hello,
> >>
> >> I've run into a CMA-related issue while testing a DMA engine driver with
> >> dmatest on a Renesas R-Car ARM platform.
> >>
> >> When allocating contiguous memory through CMA the kernel prints the
> >> following messages to the kernel log.
> >>
> >> [ 99.770000] alloc_contig_range test_pages_isolated(6b843, 6b844)
> >> failed
> >> [ 124.220000] alloc_contig_range test_pages_isolated(6b843, 6b844)
> >> failed
> >> [ 127.550000] alloc_contig_range test_pages_isolated(6b845, 6b846)
> >> failed
> >> [ 132.850000] alloc_contig_range test_pages_isolated(6b845, 6b846)
> >> failed
> >> [ 151.390000] alloc_contig_range test_pages_isolated(6b843, 6b844)
> >> failed
> >> [ 166.490000] alloc_contig_range test_pages_isolated(6b843, 6b844)
> >> failed
> >> [ 181.450000] alloc_contig_range test_pages_isolated(6b845, 6b846)
> >> failed
> >>
> >> I've stripped the dmatest module down as much as possible to remove any
> >> hardware dependencies and came up with the following implementation.
> >
> > Like Laura wrote, the message is not (should not be) a problem in
> > itself:
>
> [...]
>
> > So as you can see cma_alloc will try another part of the cma region if
> > test_pages_isolated fails.
> >
> > Obviously, if CMA region is fragmented or there's enough space for only
> > one allocation of required size isolation failures will cause allocation
> > failures, so it's best to avoid them, but they are not always avoidable.
> >
> > To debug you would probably want to add more debug information about the
> > page (i.e. data from struct page) that failed isolation after the
> > pr_warn in alloc_contig_range.
[ 94.730000] __test_page_isolated_in_pageblock: failed at pfn 6b845: buddy 0
count 0 migratetype 4 poison 0
[ 94.740000] alloc_contig_range test_pages_isolated(6b845, 6b846) failed
(-16)
[ 202.140000] __test_page_isolated_in_pageblock: failed at pfn 6b843: buddy 0
count 0 migratetype 4 poison 0
[ 202.150000] alloc_contig_range test_pages_isolated(6b843, 6b844) failed
(-16)
(4 is MIGRATE_CMA)
> If the message does not indicate an actual problem, then its printk level is
> too high. These messages have been reported when using 3.16+ distro kernels.
The messages got me worried, and if there's nothing to worry about, that's bad
:-)
--
Regards,
Laurent Pinchart
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next prev parent reply other threads:[~2014-10-28 18:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-26 21:09 CMA: test_pages_isolated failures in alloc_contig_range Laurent Pinchart
2014-10-27 20:38 ` Laura Abbott
2014-10-28 15:12 ` Laurent Pinchart
2014-10-28 12:38 ` Michal Nazarewicz
2014-10-28 13:48 ` Peter Hurley
2014-10-28 16:57 ` Michal Nazarewicz
2014-11-04 3:38 ` Peter Hurley
2014-10-28 18:59 ` Laurent Pinchart [this message]
2014-11-03 16:57 ` [PATCH] mm: alloc_contig_range: demote pages busy message from warn to info Michal Nazarewicz
2014-11-04 5:43 ` Minchan Kim
2014-11-04 12:22 ` Peter Hurley
2014-11-04 13:35 ` Michal Nazarewicz
2014-11-04 14:19 ` Peter Hurley
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